NEW YORK (AP) — Barbara Mertz, a best-selling mystery writer who wrote dozens of novels under two pen names, has died. She was 85.

Mertz died Thursday morning at her home, in Frederick, Md., her daughter Elizabeth told her publisher HarperCollins.

Mertz wrote more than 35 mysteries under the name Elizabeth Peters, including her most popular series about a daring Victorian archaeologist named Amelia Peabody. She also wrote 29 suspense novels under the pen name Barbara Michaels, and under her own name, she wrote nonfiction books about ancient Egypt.

Born Barbara Louise Gross, Mertz grew up in small-town Illinois during the Depression and went to the University of Chicago on scholarship, where she wrote on her website, “I was supposed to be preparing myself to teach — a nice, sensible career for a woman.”

But her true love was archaeology, and she soon found herself drawn to the department of Egyptology. She received a Ph.D. at the age of 23.

In the post-World War II era, she wasn’t encouraged to enter the field. “I recall overhearing one of my professors say to another, ‘At least we don’t have to worry about finding a job for her. She’ll get married,’” she wrote.

She did, and while raising two children, she decided to try her hand at mystery writing. It wasn’t until the family moved to Germany — and had the luxury of household help — that she wrote something that attracted an agent. She wrote two nonfiction books about Egypt under her own name before having her first fiction published, “The Master of Blacktower,” under the Michaels name.

“When my agent called to say I’d sold a novel, after I calmed down, she told me, ‘You’ll need a pen name,’” Mertz told The Associated Press in 1998. Barbara Michaels became her pseudonym for a series of books in the supernatural, Victorian gothic genre.

“When I wrote a different kind, the publisher said I’d need another pseudonym,” she says. “There’s always the notion people are going to use the nasty word prolific about you.”

Under the Peters name — a combination of her children’s first names — she produced several mystery series, including 19 books about Peabody. When the series began, with “Crocodile on the Sandbank” in 1975, Amelia pursued her adventures while pregnant. The series continued until her son, Ramses, was grown.

“Between Amelia Peabody and Indiana Jones, it’s Amelia — in wit and daring — by a landslide,” Paul Theroux wrote in a New York Times appreciation.

Mertz described the character to the AP as a sentimental woman who solved mysteries by guessing but nonetheless thought of herself as logical: “I want to kick her sometimes.”

As she wrote about her forceful heroine, Peters said she became more like her. Once, she said, “I was mealy mouthed, timid, never spoke up, let people push me around.”

She divorced in the 1970s, but continued her fiction writing despite financial concerns.

In 1998, Mertz received the grandmaster lifetime achievement award from the Mystery Writers of America, the top award from the mystery writers group.

“It has taken me over a quarter of a century to realize that I love to write, and that this is what I should have focused on from the beginning,” she wrote on her website.

Mertz is survived by her children, Elizabeth and Peter, and six grandchildren.